The present disclosure relates to a power amplifier.
In general, a power amplifier is a circuit which serves to amplify a low power radio frequency (RF) signal received from a transmitting terminal in a preset frequency into a high power RF signal using a nonlinear active element.
Meanwhile, in accordance with the development of communications technology, in order to prevent interference between a required high data rate and a multi-pass, digital modulation technologies have been developed.
Among these, many communications systems such as WLAN, and the like use orthogonal frequency division multiplexing (OFDM), a modulation scheme using hundreds of carriers (sub-carriers) having orthogonality to increase frequency availability. However, since frequency components are overlapped in the OFDM scheme, the amplitude of a signal may have a difference from an average magnitude of ten times at most, depending on a phase of the signal. Therefore, data loss may be prevented in a case in which the power amplifier is designed so that such a signal may also be linearly amplified.
That is, the power amplifier is designed to have an output based on maximum amplitude so that an input signal having the maximum amplitude can also be linearly amplified without being distorted. In this case, when considering that a signal section having high amplitude is significantly small as compared with signal sections having an average magnitude, a large amount of power loss may occur.
The following related art document (Patent Document 1) relates to the disclosure of operating an amplifier by turning switches connected to the respective power nodes on, depending on a signal level of an envelope using a plurality of driving amplifying stages. However, since the disclosure in the Patent Document 1 requires the plurality of amplifiers to have a plurality of loads and switches, a volume of a circuit may be increased and defects such as a voltage drop and signal distortion may be caused by resistance of the switch inserted into a power supplying unit.